Mechanical characteristics under monotonic and cyclic simple shear of spark plasma sintered ultrafine-grained nickel

Dirras, G. and Bouvier, S. and Gubicza, Jenő and Hasni, B. and Szilágyi, T. (2009) Mechanical characteristics under monotonic and cyclic simple shear of spark plasma sintered ultrafine-grained nickel. MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCURE AND PROCESSING, 526. pp. 201-210. ISSN 0921-5093

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Abstract

The present work focuses on understanding the mechanical behavior of bulk ultrafine-grained nickel specimens processed by Spark Plasma Sintering of high purity nickel nanopowder and subsequently deformed under large amplitude monotonic simple shear tests and strain-controlled cyclic simple shear tests at room temperature. During cyclic tests, the samples were deformed up to an accumulated von Mises strain of about VM = 0.75 (the flow stress were in the 650-700 MPa range), which is extremely high in comparison with the low tensile/compression ductility of this class of materials at quasi-static conditions. The underlying physical mechanisms were investigated by electron microscopy and X-ray diffraction profiles analysis. Lattice dislocation-based plasticity leading to cell formation and dislocation interactions with twin boundaries contributed to the work-hardening of these materials. The large amount of plastic strain that has been reached during the shear tests highlights intrinsic mechanical characteristics of the ultrafine-grained nickel studied here.

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